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基于3种不同应力路径下花岗岩三轴卸荷试验,研究了岩石的应力-应变全过程曲线和变形特征及其强度准则。试验结果表明,卸围压过程中,侧向应变与围压先呈线性后呈非线性关系,且其增长速率约为轴向应变增长速率的3~5倍,表现出明显的侧向扩容,其扩容程度与卸载路径有关;从不同围压与体积应变曲线所围面积可以看出,卸荷前围压越大,卸荷释放的能量越大;变形模量随围压卸载而逐渐减小,且随初始围压增大,总体上呈负指数分布趋势,且同一种卸荷应力路径时,变形模量的减小量随初始围压增大有所增大,泊松比随围压降低而不断增大,两者之间呈现明显的非线性关系;岩石破坏特征以剪切破坏为主;采用幂函数型摩尔强度准则很好反应了岩石的强度特征。研究结果对地下金属矿深部开采具有一定的指导意义和参考价值。
Based on the triaxial unloading test of granite under three different stress paths, the whole stress-strain curve and deformation characteristics of rock and its strength criterion are studied. The experimental results show that during the unloading confining pressure, the lateral strain and the confining pressure are linear firstly and then linearly, and the growth rate is about 3 ~ 5 times of the axial strain growth rate, showing a significant lateral expansion, The degree of expansion is related to the unloading path. From the area enclosed by different confining pressures and volumetric strain curves, it can be seen that the larger the confining pressure before unloading is, the larger the energy released by unloading is. The deformation modulus decreases with the unloading of the confining pressure , And with the increase of initial confining pressure, the trend of negative exponential distribution tends to be negative. With the same unloading stress path, the decrease of deformation modulus increases with the increase of initial confining pressure. Poisson’s ratio increases with the confining pressure Decreases and increases continuously with the obvious nonlinear relationship between the two. The rock failure characteristics are dominated by shear failure. The strength function of rock is well reflected by the power function type of molar strength criterion. The results of this study have certain guiding significance and reference value for the deep mining of underground metal ores.